Learn Chapter 6- Anatomy of Flowering Plants with Free Lessons & Tips

Meristems are regions of plant tissue composed of actively dividing cells. They are responsible for the growth and development of plants. There are three main types of meristems in plants, each located in specific regions and serving distinct functions:

1. Apical Meristem:

   • Location: Found at the tips of roots and shoots (terminal buds).
   • Function: Responsible for primary growth (lengthening) of plant structures in both roots and shoots. Apical meristems produce cells that differentiate into various tissues, including the epidermis, cortex, vascular tissues, and leaf primordia. In roots, apical meristems give rise to root caps, root hairs, and primary vascular tissues. In shoots, they contribute to the elongation of stems and the formation of leaves, buds, and flowers.

2. Lateral (or Cambial) Meristem:

   • Location: Located within the vascular bundles of stems and roots, known as the vascular cambium.
   • Function: Responsible for secondary growth (increase in girth) in woody plants. Lateral meristems produce secondary vascular tissues (secondary xylem and secondary phloem) that contribute to the expansion of stems and roots. The activity of the vascular cambium results in the thickening of stems and roots over time, providing structural support and increasing the transport capacity of water and nutrients. In stems, secondary growth contributes to the formation of wood, while in roots, it results in the formation of secondary xylem and phloem.

3. Intercalary Meristem:

   • Location: Found at the base of leaves (leaf axils) or internodes in certain plants, such as grasses.
   • Function: Responsible for regenerating tissues and elongating stems in grasses and other monocots. Intercalary meristems allow for the rapid regrowth of damaged or grazed plant parts. In grasses, intercalary meristems enable rapid growth and elongation of stems, facilitating recovery after grazing or mowing. They also contribute to the production of new leaves and tillers, promoting vegetative growth and overall plant development.

These different types of meristems work together to ensure the growth, development, and adaptation of plants to their environment. They play crucial roles in primary and secondary growth, tissue differentiation, and the formation of new organs and structures throughout the life cycle of plants.

Yes, I agree with the statement that cork cambium forms tissues that form the cork. Cork cambium, also known as phellogen, is a type of lateral meristem found in the bark of woody stems and roots of certain plants. It is responsible for the production of cork cells (phellem) that constitute the outer protective layer of the stem or root, known as the cork or periderm.

Cork cambium is a layer of meristematic tissue that arises from the activity of the vascular cambium or the phloem parenchyma cells. As the cork cambium undergoes cell division, it produces new cells towards both the outer and inner sides. The cells produced towards the outer side differentiate into cork cells, while those produced towards the inner side differentiate into phelloderm cells, which are part of the secondary cortex.

The cork cells produced by the cork cambium are dead at maturity and have several specialized features that make them suitable for their protective function. Cork cells are filled with suberin, a waxy substance that makes them impermeable to water and gases, providing a barrier against desiccation, pathogens, and mechanical damage. Additionally, cork cells have thick cell walls and are arranged in layers, forming a durable and protective outer covering for the plant.

Overall, cork cambium plays a crucial role in the formation of cork tissues, which serve as a protective barrier for the underlying tissues of woody stems and roots. Without the activity of cork cambium, plants would be more susceptible to damage from environmental stresses, pathogens, and physical injuries. Therefore, it is accurate to say that cork cambium forms tissues that form the cork.

Significance of Secondary Growth:

• Increased Girth: Secondary growth results in an increase in the diameter of the stem, providing structural support and stability to the plant.
• Formation of Wood: The secondary xylem produced by the vascular cambium forms the bulk of the wood, contributing to water and nutrient transport and providing mechanical strength.
• Protection: The formation of cork by the cork cambium replaces the epidermis and forms a protective outer layer (periderm), protecting the plant from physical damage, pathogens, and desiccation.
• Annual Rings: The growth rings formed by alternating layers of dense and light wood provide valuable information about the age and growth conditions of the plant, aiding in dendrochronology and environmental studies.

Anatomical Differences:

1. Vascular Bundle Arrangement:

   • Monocot Root: Vascular bundles are scattered throughout the ground tissue (cortex). They are numerous and arranged in a random pattern.
   • Dicot Root: Vascular bundles are arranged in a distinct ring or circle near the center of the root. They are usually present in the form of a single central vascular bundle or multiple bundles arranged in a ring.

2. Pith Presence:

   • Monocot Root: The pith, which is a central region of parenchyma cells, is usually absent in monocot roots.
   • Dicot Root: The pith may be present at the center of the root, consisting of parenchyma cells.

3. Cortex Thickness:

   • Monocot Root: The cortex region is usually wide and consists of several layers of ground tissue.
   • Dicot Root: The cortex region may be comparatively thinner than in monocot roots.

4. Endodermis and Pericycle:

   • Monocot Root: The endodermis and pericycle are present but may not be as well-defined as in dicot roots.
   • Dicot Root: The endodermis and pericycle are distinct layers of cells surrounding the vascular tissue, providing structural support and regulating water and nutrient uptake.

5. Epidermis:

   • Both: The outermost layer of the root, composed of a single layer of cells, known as the epidermis, functions in protection and absorption.